An interactive display device, such as a surface computing device, may interact with a user through the surface of an object, as compared to a monitor and keyboard or other such input device. Various types of touch-sensing mechanisms, including but not limited to optical and capacitive touch-sensing mechanisms, may enable the sensing of multiple temporally overlapping touches on the interactive surface. Such touch sensing mechanisms may enable the recognition of touch-based and gesture-based inputs, thereby providing for a rich user experience.